Many products have been developed and marketed for the intermittent release of a cleaning agent, disinfectant, or deodorant into a flush-type toilet tank. Typically, an inverted bottle of liquid is suspended inside the tank, so that the neck of the bottle is immersed in water. A float valve inside the neck of the bottle is held in a closed position by the water, until the toilet is flushed, causing the water level to drop, and thereby causing the valve to open. The liquid then flows from the bottle, until the tank is again full of water. The amount of liquid released from the bottle after each flush depends of course upon the time required for the tank to re-fill.
Such products are intended to last for perhaps a hundred or more flushes. But a single malfunction of the flush mechanism may cause the tank to remain empty long enough for all the liquid to escape from the bottle, before the problem is discovered. Thus it would be desirable to provide some means for limiting the amount of liquid that can escape after each flush.